Magneto-optical recording media has been in practical use as rewritable magneto-optical recording media. A problem with such conventional magneto-optical recording media is that their reproduction characteristics deteriorate as recording bits serving as magnetic recording domains have too small radii and intervals, in comparison with the radius of a light beam radiating from a semiconductor laser to be converged on the magneto-optical recording media.
The cause of such a defect is that the light beam converged on a targeted recording bit covers within its radius not only the targeted recording bit, but a neighboring recording bit as well, and that each recording bit therefore cannot be reproduced independently.
Japanese Laid-Open Patent Application No. 6-150418/1994 (Tokukaihei 6-150418) discloses a magneto-optical recording medium capable of solving the defect. The structure of the magneto-optical recording medium includes a non-magnetic intermediate layer provided between a recording layer and a reproduction layer that is in an in-plane magnetization state at room temperature and changes into a perpendicular magnetization state with a rise in temperature, wherein the recording layer and the reproduction layer are magnetostatically coupled.
The magneto-optical recording medium allows no information stored in a magnetic recording domain to be transferred to a part of the reproduction layer that is in an in-plane magnetization state as a result of low temperature, but allows the information stored in a magnetic recording domain to be transferred to a part of the reproduction layer that is in a perpendicular magnetization state as a result of a rise in temperature, thus inducing the polar Kerr effect. Therefore, the information stored in a magnetic recording domain is masked with respect to a part that is in an in-plane magnetization state, and each recording bit can be reproduced independently even if the converged light beam covers a neighboring recording bit within its radius.
Nevertheless, it has been confirmed that in order to stably performing reproduction on the magneto-optical recording medium disclosed in Japanese Laid-Open Patent Application No. 6-150418/1994 with recording bits having even smaller radii and intervals, it is necessary to generate a stronger leaking magnetic field from the recording layer and, thereby, stronger magnetostatic coupling between the recording layer and the reproduction layer. A stronger leaking magnetic field can be generated by a recording layer having a higher Curie temperature. Nevertheless, such a rise in the Curie temperature creates new problems: a resultant higher operation temperature during recording and a need for a more powerful laser beam to perform recording.